1. Field of the Invention
The invention relates to a locating device, more particularly to a locating device and a method configured to locate a pointing device operated in a three-dimensional space.
2. Description of the Related Art
A conventional pointing device (e.g., a mouse) is designed to operate on a two-dimensional surface. Recently, a three-dimensional (3D) pointing device has been developed. A 3D mouse, for example, is for controlling a cursor displayed on a screen, where a movement of the cursor is controlled by the movement of the 3D mouse within a space. The 3D mouse includes a gyroscope and an accelerator, and is capable of continuously detecting a self-motion (e.g., orientation and/or direction of the movement). A control signal is then derived by accumulating the detected self-motion, and is used for controlling the movement of the cursor. One disadvantage of such a configuration is that the accuracy is limited, and a difference between the movement of the 3D mouse and the movement of the cursor may increase with time. For example, consider a user who starts using the 3D mouse at an origin point (e.g., one that corresponds to a central point on the display unit). After a series of movement/orientations, when he/she returns the 3D mouse back to the origin point, the cursor may not be returned to the central point as desired.
One example of a 3D pointing device that may overcome the abovementioned drawback is the Wii remote (disclosed in, for example, U.S. Pat. No. 8,308,563) for the Wii console. The Wii remote includes an image pickup section, and is to be used with an optical sensor bar including a pair of spaced-apart Infrared (IR) light sources. The optical sensor bar is disposed near a display unit (e.g., a television screen) coupled to the console. When a user directs the Wii remote toward the display unit, the console is configured to control the display unit to display a cursor thereon.
The image pickup section is configured to capture a plurality of images. When one of the images contains IR light from the two IR light sources, an image processing circuit is operable to identify two bright spots in the one of the images that has higher brightness (i.e., corresponding respectively to the IR light sources), and to generate a cursor signal containing coordinate data associated with the bright spots in the one of the images. The cursor signal is then transmitted back to the console, which in turn controls the location of the cursor on the display unit based on the cursor signal.
The Wii remote may achieve higher accuracy given that the IR light sources, which serve as reference points, are fixed at same locations during operation. In such cases, whenever the Wii remote is at a certain point, the images generated by the image pickup section always have the bright spots fixed at same locations, regardless of the movements/orientations involved.
However, the Wii remote is limited to move within a certain space where light from both the IR light sources can be detected by the image pickup section. For example, when the Wii remote is swayed out of such certain space, the cursor is then rendered uncontrollable. Additionally, the image pickup section is only able to capture images with a relatively low resolution (e.g., a 480 p resolution). When it is desired to use the Wii remote on a screen supporting a higher resolution (e.g., 1080 p), the sensitivity of the cursor movement is somewhat capped.